> From: Scott Mitchell <[email protected]> > > __rte_raw_cksum uses a loop with memcpy on each iteration. > GCC 15+ is able to vectorize the loop but Clang 18.1 is not. > > Replace memcpy with direct pointer access using a packed struct with > __rte_may_alias attribute (same pattern as rte_memcpy.h). This enables > both GCC and Clang to vectorize with SSE/AVX/AVX-512 while avoiding > GCC strict-aliasing bugs without pragma workarounds. > > This patch adds comprehensive fuzz testing and updates the performance > test to measure the optimization impact. > > Performance results from cksum_perf_autotest on Intel Xeon > (Cascade Lake, AVX-512) built with Clang 18.1 (TSC cycles/byte): > > Block size Before After Improvement > 100 0.40 0.24 ~40% > 1500 0.50 0.06 ~8x > 9000 0.49 0.06 ~8x > > Signed-off-by: Scott Mitchell <[email protected]> > --- > app/test/meson.build | 1 + > app/test/test_cksum_fuzz.c | 240 +++++++++++++++++++++++++++++++++++++ > app/test/test_cksum_perf.c | 2 +- > lib/net/rte_cksum.h | 22 ++-- > 4 files changed, 255 insertions(+), 10 deletions(-) > create mode 100644 app/test/test_cksum_fuzz.c > > diff --git a/app/test/meson.build b/app/test/meson.build > index efec42a6bf..c92325ad58 100644 > --- a/app/test/meson.build > +++ b/app/test/meson.build > @@ -38,6 +38,7 @@ source_file_deps = { > 'test_byteorder.c': [], > 'test_cfgfile.c': ['cfgfile'], > 'test_cksum.c': ['net'], > + 'test_cksum_fuzz.c': ['net'], > 'test_cksum_perf.c': ['net'], > 'test_cmdline.c': [], > 'test_cmdline_cirbuf.c': [], > diff --git a/app/test/test_cksum_fuzz.c b/app/test/test_cksum_fuzz.c > new file mode 100644 > index 0000000000..839861f57d > --- /dev/null > +++ b/app/test/test_cksum_fuzz.c > @@ -0,0 +1,240 @@ > +/* SPDX-License-Identifier: BSD-3-Clause > + * Copyright(c) 2026 Apple Inc. > + */ > + > +#include <stdio.h> > +#include <string.h> > + > +#include <rte_common.h> > +#include <rte_cycles.h> > +#include <rte_hexdump.h> > +#include <rte_cksum.h> > +#include <rte_malloc.h> > +#include <rte_random.h> > + > +#include "test.h" > + > +/* > + * Fuzz test for __rte_raw_cksum optimization. > + * Compares the optimized implementation against the original > reference > + * implementation across random data of various lengths. > + */ > + > +#define DEFAULT_ITERATIONS 1000 > +#define MAX_TEST_LEN 65536 /* 64K to match GRO frame sizes */ > + > +/* > + * Original (reference) implementation of __rte_raw_cksum from DPDK > v23.11. > + * This is retained here for comparison testing against the optimized > version. > + */ > +static inline uint32_t > +__rte_raw_cksum_reference(const void *buf, size_t len, uint32_t sum) > +{ > + const void *end; > + > + for (end = RTE_PTR_ADD(buf, RTE_ALIGN_FLOOR(len, > sizeof(uint16_t))); > + buf != end; buf = RTE_PTR_ADD(buf, sizeof(uint16_t))) { > + uint16_t v; > + > + memcpy(&v, buf, sizeof(uint16_t)); > + sum += v; > + } > + > + /* if length is odd, keeping it byte order independent */ > + if (unlikely(len % 2)) { > + uint16_t left = 0; > + > + memcpy(&left, end, 1); > + sum += left; > + } > + > + return sum; > +} > + > +static void > +init_random_buffer(uint8_t *buf, size_t len) > +{ > + size_t i; > + > + for (i = 0; i < len; i++) > + buf[i] = (uint8_t)rte_rand(); > +} > + > +static inline uint32_t > +get_initial_sum(bool random_initial_sum) > +{ > + return random_initial_sum ? (rte_rand() & 0xFFFFFFFF) : 0; > +} > + > +/* > + * Test a single buffer length with specific alignment and initial sum > + */ > +static int > +test_cksum_fuzz_length_aligned(size_t len, bool aligned, uint32_t > initial_sum) > +{ > + uint8_t *data; > + uint8_t *buf; > + size_t alloc_size; > + uint32_t sum_ref, sum_opt; > + > + if (len == 0 && !aligned) { > + /* Skip unaligned test for zero length - nothing to test */ > + return TEST_SUCCESS; > + } > + > + /* Allocate exact size for aligned, +1 for unaligned offset */ > + alloc_size = aligned ? len : len + 1; > + if (alloc_size == 0) > + alloc_size = 1; /* rte_malloc doesn't like 0 */ > + > + data = rte_malloc(NULL, alloc_size, 64); > + if (data == NULL) { > + printf("Failed to allocate %zu bytes\n", alloc_size); > + return TEST_FAILED; > + } > + > + buf = aligned ? data : (data + 1); > + > + init_random_buffer(buf, len); > + > + sum_ref = __rte_raw_cksum_reference(buf, len, initial_sum); > + sum_opt = __rte_raw_cksum(buf, len, initial_sum); > + > + if (sum_ref != sum_opt) { > + printf("MISMATCH at len=%zu aligned='%s' initial_sum=0x%08x > ref=0x%08x opt=0x%08x\n", > + len, aligned ? "aligned" : "unaligned", > + initial_sum, sum_ref, sum_opt); > + rte_hexdump(stdout, "failing buffer", buf, len); > + rte_free(data); > + return TEST_FAILED; > + } > + > + rte_free(data); > + return TEST_SUCCESS; > +} > + > +/* > + * Test a length with both alignments > + */ > +static int > +test_cksum_fuzz_length(size_t len, uint32_t initial_sum) > +{ > + int rc; > + > + /* Test aligned */ > + rc = test_cksum_fuzz_length_aligned(len, true, initial_sum); > + if (rc != TEST_SUCCESS) > + return rc; > + > + /* Test unaligned */ > + rc = test_cksum_fuzz_length_aligned(len, false, initial_sum); > + > + return rc; > +} > + > +/* > + * Test specific edge case lengths > + */ > +static int > +test_cksum_fuzz_edge_cases(void) > +{ > + /* Edge case lengths that might trigger bugs */ > + static const size_t edge_lengths[] = { > + 0, 1, 2, 3, 4, 5, 6, 7, 8, > + 15, 16, 17, > + 31, 32, 33, > + 63, 64, 65, > + 127, 128, 129, > + 255, 256, 257, > + 511, 512, 513, > + 1023, 1024, 1025, > + 1500, 1501, /* MTU boundaries */ > + 2047, 2048, 2049, > + 4095, 4096, 4097, > + 8191, 8192, 8193, > + 16383, 16384, 16385, > + 32767, 32768, 32769, > + 65534, 65535, 65536 /* 64K GRO boundaries */ > + }; > + unsigned int i; > + int rc; > + > + printf("Testing edge case lengths...\n"); > + > + for (i = 0; i < RTE_DIM(edge_lengths); i++) { > + /* Test with zero initial sum */ > + rc = test_cksum_fuzz_length(edge_lengths[i], 0); > + if (rc != TEST_SUCCESS) > + return rc; > + > + /* Test with random initial sum */ > + rc = test_cksum_fuzz_length(edge_lengths[i], > get_initial_sum(true)); > + if (rc != TEST_SUCCESS) > + return rc; > + } > + > + return TEST_SUCCESS; > +} > + > +/* > + * Test random lengths with optional random initial sums > + */ > +static int > +test_cksum_fuzz_random(unsigned int iterations, bool > random_initial_sum) > +{ > + unsigned int i; > + int rc; > + > + printf("Testing random lengths (0-%d)%s...\n", MAX_TEST_LEN, > + random_initial_sum ? " with random initial sums" : ""); > + > + for (i = 0; i < iterations; i++) { > + size_t len = rte_rand() % (MAX_TEST_LEN + 1); > + > + rc = test_cksum_fuzz_length(len, > get_initial_sum(random_initial_sum)); > + if (rc != TEST_SUCCESS) { > + printf("Failed at len=%zu\n", len); > + return rc; > + } > + } > + > + return TEST_SUCCESS; > +} > + > +static int > +test_cksum_fuzz(void) > +{ > + int rc; > + unsigned int iterations = DEFAULT_ITERATIONS; > + printf("### __rte_raw_cksum optimization fuzz test ###\n"); > + printf("Iterations per test: %u\n\n", iterations); > + > + /* Test edge cases */ > + rc = test_cksum_fuzz_edge_cases(); > + if (rc != TEST_SUCCESS) { > + printf("Edge case test FAILED\n"); > + return rc; > + } > + printf("Edge case test PASSED\n\n"); > + > + /* Test random lengths with zero initial sum */ > + rc = test_cksum_fuzz_random(iterations, false); > + if (rc != TEST_SUCCESS) { > + printf("Random length test FAILED\n"); > + return rc; > + } > + printf("Random length test PASSED\n\n"); > + > + /* Test random lengths with random initial sums */ > + rc = test_cksum_fuzz_random(iterations, true); > + if (rc != TEST_SUCCESS) { > + printf("Random initial sum test FAILED\n"); > + return rc; > + } > + printf("Random initial sum test PASSED\n\n"); > + > + printf("All fuzz tests PASSED!\n"); > + return TEST_SUCCESS; > +} > + > +REGISTER_FAST_TEST(cksum_fuzz_autotest, true, true, test_cksum_fuzz); > diff --git a/app/test/test_cksum_perf.c b/app/test/test_cksum_perf.c > index 0b919cd59f..6b1d4589e0 100644 > --- a/app/test/test_cksum_perf.c > +++ b/app/test/test_cksum_perf.c > @@ -15,7 +15,7 @@ > #define NUM_BLOCKS 10 > #define ITERATIONS 1000000 > > -static const size_t data_sizes[] = { 20, 21, 100, 101, 1500, 1501 }; > +static const size_t data_sizes[] = { 20, 21, 100, 101, 1500, 1501, > 9000, 9001, 65536, 65537 }; > > static __rte_noinline uint16_t > do_rte_raw_cksum(const void *buf, size_t len) > diff --git a/lib/net/rte_cksum.h b/lib/net/rte_cksum.h > index a8e8927952..30eff6cbaa 100644 > --- a/lib/net/rte_cksum.h > +++ b/lib/net/rte_cksum.h > @@ -42,15 +42,19 @@ extern "C" { > static inline uint32_t > __rte_raw_cksum(const void *buf, size_t len, uint32_t sum) > { > - const void *end; > - > - for (end = RTE_PTR_ADD(buf, RTE_ALIGN_FLOOR(len, > sizeof(uint16_t))); > - buf != end; buf = RTE_PTR_ADD(buf, sizeof(uint16_t))) { > - uint16_t v; > - > - memcpy(&v, buf, sizeof(uint16_t)); > - sum += v; > - } > + /** > + * unaligned_uint16_t triggers GCC bug where buf memory may not > be > + * initialized. rte_uint16_alias avoids strict aliasing bugs. > + */ > + struct __rte_packed_begin rte_uint16_alias { > + uint16_t val; > + } __rte_packed_end __rte_may_alias; > + > + /* Process uint16 chunks to preserve overflow/carry math. > GCC/Clang vectorize the loop. */ > + const uint16_t *buf16 = (const uint16_t *)buf; > + const uint16_t *end = buf16 + (len / sizeof(uint16_t)); > + for (; buf16 != end; buf16++) > + sum += ((const struct rte_uint16_alias *)buf16)->val; > > /* if length is odd, keeping it byte order independent */ > if (unlikely(len % 2)) { > -- > 2.39.5 (Apple Git-154)
Acked-by: Morten Brørup <[email protected]>
